Such incidents cause grave scandal among ordinary members of the Church – not least because both Kaine and Biden are often described by the media as “devout Catholics”.

These incidents present Church leaders with a dilemma. But at least one US bishop has reached firm conclusions. In a new book-length interview (Hope for the World, Ignatius Press / Gracewing, £9.99), Cardinal Raymond Burke relates that in 2004, as Bishop of La Crosse, he publicly challenged Catholic politicians. Cardinal Burke instructed them “to make their public actions consistent with the moral law taught by the Church; otherwise it would no longer be possible for them to receive Holy Communion.”

These words are all the more striking because, in the rest of the book, the cardinal’s replies to the interviewer Guillaume d’Alencon tend to be cautious, brief and predictable.

But then on this matter Cardinal Burke has been forced to defend his position. In 2004, when he was transferred from La Crosse to the Archdiocese of St Louis, he was told by some of his confreres “that we must not punish Catholic politicians whose political activity [is] disordered” as the bishops’ conference had “not yet made a pronouncement on this subject.”

Cardinal Burke replied in forthright fashion, pointing out that the bishops’ conference can never replace the mission of the bishop in his own diocese, where his task is to govern his flock and proclaim the faith. He added, “At the last judgement, I will appear before the Lord, and not before the conference of bishops.”

The same straightforward thinking, incidentally, appears in the cardinal’s comments on Islam. Rather than echoing conventional Catholic wisdom, which keeps telling us how peaceful Islam is, he says that “Islam is not just another religious practice that can coexist in harmony with other religions… In reality there is no place for other religions, even though they may be tolerated, as long as Islam has not succeeded in establishing its sovereignty.” He stresses that Christians need to know the radical differences between Islam and Christianity, concluding “If you really understand Islam, you understand that the Church really should be afraid of it.”

This statement chimes in with the instincts of many ordinary Catholics who think such “radical differences” should be given a more public voice within the Church.

In both matters, Cardinal Burke provides the kind of strong spiritual leadership that Catholics long for and which is clearly lacking among some of his fellow bishops. Their silence sounds like cowardice; it is certainly no kindness to men like Biden and Kaine who appear to be simply ignorant of precisely what the cardinal emphasises: “the moral law taught by the Church”.